The reason why artificial flavors in general are different, is that a plant's flavor is made of a lot of different chemicals, and artificial flavorings only include the most noticeable (and least expensive) ones - so all the subtleties get left out.

No idea if the change of banana varieties also affects it, or not.

I don't know any source but I have seen that comment mentioned in every banana related blog post I ever read.

Anecdotal evidence: A friend that traveled to Panama tasted the Gross Michel and said that the flavor is closer.